The present invention is directed to a novel sheet registration device for a sheet registration apparatus and has particular application in an electrostatographic printing apparatus.
In the process of electrophotographic printing, a photoconductive surface is charged to a substantially uniform potential. The photoconductive surface is image wise exposed to record an electrostatic latent image corresponding to the informational areas of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, a developer material is transported into contact with the electrostatic latent image. Toner particles are attracted from the carrier granules of the developer material onto the latent image. The resultant toner powder image is then transferred from the photoconductive surface to a sheet of support material and permanently affixed thereto.
This process is well known and useful for light lens copying from an original and printing application from electronically generated or stored originals, and in ionography.
In U.S. Pat. No. 4,541,626 to Millen a sheet registration apparatus and device are described wherein a hub having an axis of rotation and a plurality of resilient blades arranged in radial planes passing through the axis and extending in the direction of the axis beyond one end of the hub towards sheet-engaging tips lying in a common plane normal to the axis is used to wipe over a limited arc of rotation against a sheet on a surface to urge it towards a registration stop. This device turns and positions a sheet into a corner registration so it can be finished by stapling and binding and is used in the Xerox 1075, 1090 and 5100 duplicators. The resilient blades are made of a conventional polyester polyurethane filled with carbon black. While capable of performing adequately they suffer certain deficiencies, particularly with respect to the variation in their mechanical properties with changes in temperature and relative humidity. The mechanical properties such as resiliency, wear, compression set and tensile set are dynamic properties varying with changes in temperature and relative humidity, thereby, providing unstable sheet registration performance paper edge alignment difficulties and misstapling.
In addition, the blades have a tendency, particularly in the warmer and more humid environments, to make black marks on the sheets being registered.
Accordingly, there is a need for an improved material having a more stable response in mechanical properties, particularly resiliency, to variations in temperature and relative humidity and in particular, having better wear and compression set characteristics as well as not making black marks on paper.